Health Behaviour, Dietary Supplements and Obesity: A Propensity Score Matching Approach

Despite significant efforts to inform and educate consumers across North America on healthy eating through "easy to follow" dietary guidelines, diet related non-communicable diseases are on the ascendancy. The objective of this thesis is to use the National Health and Nutrition Examination Survey (NHANES) 2007--2008 data to determine how dietary supplement users may differ from nonusers in body mass index (BMI) outcome and how the extent of dietary supplement intake through its effect on diet quality may affect BMI. Propensity Score Matching was used to account for the possible selection bias and endogeneity of the self-reported dietary supplement intake and treatment outcome variable in the NHANES data. The results suggest that the typical dietary supplement taker is a white female of higher socioeconomic status. Other results show that supplement consumption may be associated with significant lower BMI outcomes. However, we fail to confirm a linear relationship between the number of supplements consumed and BMI. Policy makers should intensify the public education on fruit and vegetable consumption to ensure that people largely meet their nutrient needs from food instead of dietary supplements due to the potential negative effect of overuse of dietary supplements.